Introduction to the Exposure Triangle
As promised in the previous tips, this one will introduce you what may be the most valuable thing a novice photographer can learn. It's called the Exposure Triangle and it's the simplest and best way to understand exposure.
STOP! If you haven't read the articles below, I highly recommend doing so before you proceed with this one, since you'll need to understand these elements of exposure first:
Aperture 101 Shutter Speed 101 Understanding ISO
What's the Exposure Triangle?
The Exposure Triangle describes the way that shutter speed, aperture and ISO work together in your camera to determine the exposure, meaning the overall lightness or darkness, of a photo. By understanding the relationship between these elements and how they affect your photos, you'll be one step closer to taking full control of your images. You don't have to shoot in manual mode to use it, but learning to use it should help you reach the point that you can turn that mode dial to "M" with confidence.
(Success Tip #1: Find out how even hobbyists can turn photos in to profits.)
How does the Triangle work?
We'll use the diagram at the top of this article to illustrate how the Triangle works. As you can see, it shows the 3 elements of exposure, how each one affects your images and and how they affect exposure. For example, at the base of the triangle, you'll see that as the ISO setting increases, so do both light sensitivity and noise, while an increase in shutter speed decreases the duration of the light striking the sensor and the possibility of motion blur. On the other hand, increasing the aperture size increases the quantity of light passing to the sensor, while decreasing depth of field.
The triangle simply represents the connection between the elements. If we consider the area of the triangle to be the "correct" exposure, and the outermost labels the factors that affect exposure, you can see that in order to maintain it, any adjustment to one side will require a corresponding adjustment to one or both of the other sides. The triangle sides don't have to remain equal, and the triangle doesn't have to stay straight. The important thing is that the exposure value remains the same.
How do I use it?
Putting the Exposure triangle to work is a simple process. First, decide what's most important in your image. Find the component that controls that aspect and adjust it, then adjust one or both of the others to bring the exposure back into balance.
For instance, let's say you're shooting a landscape shot and you want maximum depth of field. The diagram shows that you'll want to decrease your aperture size, so you set it at F/22. Now, that's going to change the area of the triangle, so you'll need to make another adjustment. You can either extend the duration of light by lowering your shutter speed or increase he sensitivity by increasing the ISO setting. You may also split the adjustment between the two other sides.
If you're shooting without a tripod, your next adjustment might be to raise the ISO setting, since a slower shutter speed will increase the possibility of motion blurring. If you have a tripod, a slower shutter speed and lower ISO setting will decrease the noise in your shot.
What if I don't want the "correct" exposure?
There will be times when you'll want to "step outside the box" on this, as with any guidelines or tools. Making adjustments to deliberately underexpose or overexpose your images is just as easy, once you've learned how the Triangle works.
(Success Tip #2: How to learn photography when you don't have a lot of spare time)
Congratulations!
You now know how your camera calculates exposure when you shoot in any autoexposure mode. Now that you have the tool, get out there and try doing it yourself. Go on, switch to "M" and give it a try!
